Ecological Study Of Radix Auricularia With Ceratophyllum Demersum, Potamogeton Crispus In The Baiyangdian Lake

Submerged plants which can sustain the stability of lake ecosystem play an important part in the freshwater ecosystem. It is well documented that herbivorous invertebrates can influence relative abundance and diversity of macrophyte species in lake communities. Freshwater plants may have wide relationships with numerous kinds of invertebrate herbivores, including crayfish, crab and mollusk.Studies about relationships between snails and submerged plants are a hotspot in this field. There are various kinds of theories and hypothesizes about relationships between snails and submerged plants, such as:mutualistic Relationship between snails and plants, theroy of resource availability, carbon nitrogen Balance hypothesis. Owing to the lack of research in the freshwater ecosystem, It needs to test and revise the correctness and applicability of these theories and hypothesisCeratophyllum demersum and Potamogeton crispus which functions to purify water and to supply life place and food for creatures are the dominating submerged plants in the Baiyangdian lake.Radix auricularia is the dominating plant-grazed snail in the Baiyangdian lake.So it is important to study the herbivory relationships between Radix auricularia and Ceratophyllum demersum,Potamogeton crispus. It also provides a proof of relationship between Snails and Plants.This research discovered that the snail could graze two species of submerged plants by unselectivity herbivory experiment, which was not similar to other studies. Snail prefered Potamogeton crispus whatever through selectivity herbivory experiment. It explained that Radix could increase the abundance of Ceratophyllum demersum. The research tried to find out the reasons of making difference between these two species of plants by determinating the protein, liquid, water content and energy content of plants, organism of plants, the consistency of N and P, diversity of bacteria too.Research discovered that there were not significant differences in the protein,liquid, water,energy content of plants, organism of plants, which meant that the two species of plants had the same tactics in anti-herbivory. It was in line with some scholars’results.Research showed that experimental group of Potamogeton crispus releaseed more nitrogen and phosphorus.This was due to Potamogeton crispus ated more seriously. Also this had relation with snails’release level.Bacteria diversity was determined. The gross bacteria biomass and the diversity in the plants were higher than that in water. And there were signigicant differences between two species of plants in the gross number of bacteria and the level of diversity. The gross number of bacteria and the level of diversity influenced in palatability. the result showed that bacterial D may be a kind of food attractant for snails.All the resultd showed that there was onesidedness in the theory of mutualistic relationship between snails and plants. The snails grazed epiphytes on the plant, but also plants themselves. Those herbivory can decline the diversity of submerged plants.There were not differences in the protein,liquid, water content,energy of plants, organism of plants, which meant that the two species of plant had the same tactics by C:N and the distribution of energy in anti-herbivory. And snails enhanced the released level of N and P, so as to intensify the death of plants.That means herbivory can reduce the biomass of Potamogeton crispus so thar Ceratophyllum demersum will become the dominant species. Maybe there were a positive relationship between bacterial D and palatability. If Porphyrobacter can be pull into plants by people, maybe palatability will down to decline herbivory. It is a way to protect submerged plants’abundance and diversity. And this is ought to the next step.